Remember that a 2 gang switch is just like any other one gang switch. The only difference is they are 2 switches bundled together side by side and each of the switches are in fact just like any one gang switch. If anyone knows how to terminate a one gang switch, they should have no problem terminating a 2 gang switch or a three gang switch for that matter.
As previously discussed, the terminals of switches are indicated by the signs, L1 and L2 where L1 denotes the incoming current and L2 denotes the outgoing. The incoming mean the wire that is bringing the current from the Mains to the switch and out going means the current that goes to the light when the switch is in the ON position.
A switch is just a device you use to cut of the current from the incoming and the outgoing. When the switch is in the ON position, it means the terminals, L1 and L2 are closed therefore allowing current to pass through. The opposite happens when the switch is in the “OFF” position. It is all made possible by springs, therefore a switch, be it one gang, two gang or even three gang is a mechanical device and mechanical devices will suffer wear and tear after prolonged use. There will be a time when you need to replace those switches.
Replacing a one gang switch is a straightforward affair. When dismantling the old switch, just remember which wire was from the L1 terminal and which is from the L2 terminal. All you have to do is to terminate the wires exactly the way it was before. L1 to L1 and L2 to L2. However when it comes to a 2 gang switch, you will notice another short piece of wire connected together with the incoming wire terminated at L1. This short piece will be connected to the L1 terminal of the other switch in within the 2 gang switch. This piece of short wire is also an incoming wire . The only difference is it gets it’s current from the wire that comes from the Mains. You can also run this wire back to the Mains and it will work exactly the same, but why waste a whole length of wire when there is already a ready source just next to it?
Once you understand this point, you will have no problems terminating any multi gang switch. It can even be a 4 gang switch and all you have to do is to keep connecting the the incoming wire to all the other L1 Terminals. When that is done, all the remaining wires are the outgoing wires and all you have to do is to terminate them individually to each of the switches.